1. Field of the Invention
The present invention relates to a sewing machine with pattern stitching function and more particularly relates to pattern data which may be selectively used to form an optional stitch pattern including a plurality of pattern elements, the pattern data being optionally modified with respect to each of the pattern elements.
2. Prior Art
It has been generally prevalent that the sewing machine is operated under control of a zigzag stitch producing mechanism and a work feeding amount adjusting mechanism to form a pattern of zigzag stitches. Namely, according to the conventional sewing machine with pattern stitching function, the pattern data are particularly provided to each of the different patterns to be selectively formed. Therefore, in case a pattern is modified or varied, it is required that the pattern data is modified or varied accordingly in its entirety.
However, actually it is often required to modify or vary a pattern, particularly as to the individual pattern elements which form the pattern, instead of modifying the entire pattern.
In this case, it may be considered that the pattern is divided into the elements to be individually modified or varied so that the modified or varied pattern elements may be reconstructed into a pattern. It is, however, very difficult to position the individual pattern elements so as to form a single pattern.
The invention has been provided to eliminate the defects and disadvantages of the prior art. It is, therefore, an object of the invention to provide a sewing machine with pattern stitching function which may be operated under control of pattern data to form a pattern of a plurality of different pattern elements, the pattern data being modified or varied with respect to each of the pattern elements.
For attaining the object of the invention, the sewing machine substantially comprises a needle mechanism including a vertically reciprocating needle and a work feeding mechanism including a feed dog for transporting a work relative to the needle so as to be stitched, the needle mechanism being swingable transversely of the direction in which the work is transported, the needle mechanism and the work feeding mechanism being operated under control of pattern data to form a pattern of stitches on the work, means for giving pattern data for producing a stitch pattern composed of a plurality of pattern elements, means for modifying the pattern data for each of said pattern elements.
With combination of the elements including the means for modifying the pattern data for each of said pattern elements, the variation of a stitch pattern may be increased. Further, since the pattern is formed by a set of pattern data, the stitching position may be easily changed.
According to a preferred embodiment, the pattern may be composed of a portion of dense zigzag stitches and a portion of one or more straight stitches. Therefore, in case the pattern data for modifying the straight stitch portion is optionally changed, the pattern may be modified in so many ways. It is needless to say that the zigzag stitch portion may be modified, instead of the straight stitch portion.
The pattern of dense zigzag stitches may be replaced by another pattern of other stitches than the zigzag stitches.
Preferably, the pattern data may includes the data for controlling the zigzag stitch width, the data for controlling the work feeding amount and the data for controlling the thread tension. The thread tension may be changed for the zigzag stitch portion and for the straight stitch portion to obtain an optimal stitch pattern.